Agricultural crop harvesting implements, called self-propelled combines, have wide headers that pick up and cut the crops for delivery to a separating unit. The wide headers must be removed from the combine vehicle to permit the combine to be transported down a roadway or lane from field to field. Wagons have been developed to mount and carry combine headers. An example of a combine header carrier for a transport vehicle is disclosed by W. W. Bruns in U.S. Pat. No. 4,834,598. The transport vehicle is a conventional trailer that includes a reach assembly connecting front and rear bolsters that are associated with front and rear wheels. The bolsters serve as supports for both the back stops and the transverse support beam that hold the header. The back stops are not longitudinally adjustable relative to the bolsters. A linkage is used to adjust the vertical height of the header support rail. The back stop is transversely adjustable on a support beam attached to the bolster. The adjustments must be made to permit the carrier to accommodate different sizes and types of combine heads. The present invention is a further improvement of a vehicle to transport grain combine headers and row crop headers.